Process for the manufacture of products made from cellulose derivatives



Patented July 5, 1938 PROCESS FOR THE MANUFACTURE OF PRODUCTS MADE FROM CELLULOSE DE- RIVATIVE S Ernst Berl, Pittsburgh, Pa.

No Drawing. Application May 3, 1934, Serial No. 723,705

1 Claim.

' The present invention relates to a process of manufacturing products made from cellulose derivatives.

' It is an object of, the present invention to provide a processforv the manufacture of products such as threads, ribbons, films, etc., made from solutions or swellings of cellulose esters or cellulose'ethers or mixtures. thereof.

I It is another object of the invention to provide. a process which produces cellulosic threads having increased strength and lower elongation.

It is also within the. contemplation of the in- ,ventionto. provide a process which produces very fine cellulosic filaments.

Other objects and advantages will become apparent from the following description.

Broadly stated, the present invention contemplates the introduction of solutions or swellings of the cellulose derivatives into a coagulating bath in order to be solidified. It is preferred to provide a' coagulating bath containing strong coagulating salts of. alkalis and alkaline earths, such as nitrates, chlorides, acetates, formates, oxalates, etc. Such a bath may also contain swelling materials suchas alcohol, acetone, ether, acetic acid, formic acid, .phosphoric acid, etc. After the coagulation, the. coagulated product. is passed into and. through a softening bath for treatment. with swelling or softening agents, such, as. alcohol, acetone, ether, acetic acid, formic acid, etc. In thesofteningbath, the fcoagulatedproductv is. converted; into a plastic state and is subjected to a stretching process.

The stretching process. may take place before, during or after the softening of the coagulated products. I have obtained satisfactory results by beginning to stretch the fibers before introducing them into the softeningor swelling bath and in addition subjecting the thread to a stretching action of suitable intensity while the thread is passing through and leaving the softening or swelling bath.

O In carrying the invention into practice, it is preferred to dissolve the cellulose derivatives to betreated, for instance, cellulose nitrate in a solvent, such as a mixture of alcohol and ether which may contain one volumeof 96% alcohol and one volume of commercialether. The solu tion known as collodium is introduced into a coagulation bath which may consist, for instance, of about 40 to 75% per Weight of 96% alcohol containing ammonium nitrate, upto say about of the maximum saturation. The foregoing operation causes the quick coagulation or the collodiu'in' and the 'formation of threads.

swelling means.

The thread is passed into a second bath containing swelling or softening agents. Upon softening, the thread is stretched in the swelling bath. The softening bath mayconsist, for instance, of about 40 to 60% volume of alcohol.

By following the foregoing procedure, it is possible to produce strong threads of the finest structure from cellulose nitrate.

Instead of cellulose nitrate, other cellulose v derivatives may be treated. For instance, solutions of cellulose acetate in acetic acid, formic acid'or in acetone or mixtures of solvents, may be spun wet by using the aforesaid coagulation and softening baths.

The process may be modified in different respects. For instance, the first bath (coagulation bath) may be joined with other baths in such a waythat the second bath contains besides the swelling agents, coagulating means in suitable quantities while the third bath may contain only One can also proceed in such a way that the products are passed successively through baths which contain coagulating means or swelling means or mixtures of the same. One can also proceed in such a manner that one passes the products consecutively through baths of different concentration. For instance, the first swelling bath may contain a mixture of more or less concentrated acetic acid and alcohol; the

second bath may be connected to it which may diluted acetic acid with addition of sodium acetate, etc. One use therefore, substances which combine coagulating and swelling actions, such as phosphoric acid in. a solution, f. i. of 40 to 50%.

The process of stretching may also take place according to ones need. For instance, in such a manner that the threads upon leaving the coagulating bath are stretched; thereupon they may undergo another stretching process in the swelling bath and upon leaving the swelling bath may be stretched still further. 1

It has been found that this process has its advantage in many directions. Due to the prompt treatment of the products with suitable coagulating means, they receive such a solidification that the wet spinning process may be carried out very quickly and the thread may be pulled rapidly without any danger of damage to it. Through the following softening of the filament, which was first solidified, combined with the stretching of thesame during or in connection with the 55 softening process, it is possible to increase considerably the dry and wet strength of the thread.

It has been noted that in using this method not much stretching is required in order to attain the desired parallel arrangement of the micelles and the desired increase in dry and wet strengths.

It is to be observed that by the use of the foregoing method, it is possible to produce products of very good qualities particularly with respect to strength from solutions or swellings of cellulose acetates in acids, especially acetic acid. Heretofore, this has not been possible. Moreover, the present process has the important advantage .of using not only lower acetylated and acetonesoluble acetates, but also high acetylated, almost triacetylated cellulose acetates. This makes reacetylation unnecessary and structures are produced which either do not swell at all or very little in water which is just the opposite of the structures formed from acetone-soluble products. The coagulation bath may contain not only distinct coagulation agents which may consist preferably of salt solutions, but also swelling agents, such as acetone, alcohol, acetic acid, formic acid, etc. In this manner, the coagulation bath may be regulated to a desired degree of action and coagulation which is too strong may be avoided. The coagulation may also take place by degrees. In other words, the solution or swelling to be treated is first introduced into a bath which contains, for instance, only swelling agents, such as watery alcohol. The structures are then passed into a second bath which contains precipitating salts alone or in combination with swelling agents. The coagulated product is next introduced into a softening bath while being subjected to stretching. The softening bath may contain not only swelling agents but also small quantities of precipitating agents.

For carrying the invention into practice, one may also use such agents which have at the same time precipitating and swelling properties, such as phosphoric acid for instance. One may use diluted phosphoric acid of about 30% strength, for instance, as a precipitating agent whereby threads are produced which are more or less swollen. On the other hand, threads precipitated in salt baths can be brought into a state of swelling again by a subsequent treatment with phosphoric acid of about 50% strength, for instance. In this manner, the threads are prepared for the stretching process to be subsequently applied. 'Acetic acid may be used in place of phosphoric acid. This acid acts either in a'swelling or in a precipitating direction according to its strength.

The spinning solution, for instance, may be introduced into phosphoric acid of about 30 to about 45%. The structure thus produced may be exposed to a stretching either in the precipitating bath, the swelling bath or on its way to the softening bath. Thereupon the coagulated'structures may be made plastic in the softening bath, which may consist, for instance, of alcohol of about 4.0 to strength and are stretched. The

spinning solution may also be first passed into a watery solution nearly saturated with ammonium nitrate and containing about 50% alcohol, The structures are exposed to stretching and afterwards are softened in phosphoric acid of about 40 to about 60% strength and thenthey are stretched again.

In carrying out the present process practically, the operations are conducted in such a manner that the thread produced in the precipitation 'etc.

bath will have such a strength that the thread 7 may be pulled with an adequate speed. The precipitation bath may consist for instance of 'a concentrated watery solution of ammonium nitrate with addition of suitable quantities of swelling means, such as alcohol, methanol, acetone, To the precipitating bath may be added substances such as dextrose, cane sugar, molasses, thick sulfite liquor, etc. which increase the viscosity many times above the water. The pull ing 011' is carried out in such a manner that little stretching occurs. Thereupon, the thread is brought to the desired grade of plasticity by per denier and a wet strength of about 1.4 to 1.6 g.

per denier.

For the purpose of giving those skilled in the art a better understanding of the invention, the following illustrative examples will be given.

Examples 1. In a precipitating bath, which consists of about 17 to 23% ammonium nitrate, about 24- 30% water, and about 50 to 56% alcohol, a solution of cellulose nitrate in a mixture of equal volumes of alcohol and ether with a speed of about 30 m. per minute is spun through a nozzle having '75 holes of about 0.07 mm. diameter. Thesoftening bath in which the spun threads are entered from the spinning bath in order to be stretched there or in connection therewith, contains 80% alcohol. The titre of the artificial silk produced is denier which corresponds to a single titre oi 1.47 denier. The dry strength of the product received is 2.60 g. per denier, the wet strength 1.50 g. per denier, the plastic tension which is also known as elasticity is 10% and the stretching is about 12%.

Threads which have not been stretched give a titre of denier of the spun silk which corresponds to 1.68 denier for a single titre by using the same nozzle with 7,6 orifices of about 0.07 mm'. diameter and the same pulling off speed. The dry strength of threads produced without stretching is 1.18 g. per denier; the wet strength 0.48'g. per denier and the plastic tension or elasticity is 21%. In comparing these figures with the ones mentioned above for stretched threads, one will clearly see the results which may be obtained if the process is carried out according to the present invention. 7

2. In a precipitating bath, which has the composition of the one mentioned above, a spinning solution described in Example 1 was passed through a nozzle of hundred orifices of about 0.07 mm. For the softening bath, a composition of about'17% ammonium nitrate, about 25% water, about 56% alcohol and about 2% ether was used.

The titre of the silks'obtainedwas 80denier;,

the single titre 0.8 denier. The dry strength was 2.56 g. per denier; the wet strength 1.54 g. per

the single titre 1.2 denier, the dry strength 2.3 g. per denier and the wet strength 1.1 g. per denier.

4. Cellulose acetates, which are dissolved in acetic acid or formic acid or other solvents, are entered into a bath of the composition of the baths described in Examples Nos. 1 and 2. One

can add to the solution of the acetate, diluting substances, such as alcohol, before spinning. The precipitation bath may contain acetates or formates alone or with addition of alcohol instead of a solution of ammonium nitrate. Instead of alcohol, diluted acetic acid or diluted formic acid or diluted acetone and similar substances or their mixtures may be used. For instance, a bath composed of about 22% acetic acid, about 15% alcohol, about 8% sodium acetate and about 55% water can be used with great advantage. The structure formed in the precipitation bath is entered into another bath or baths which contain swelling agents, such as acetic acid, alcohol and water. During and after passing through the softening bath, the products are exposed to a stretching process. Threads formed according to this process may be wound upon bobbins or they may be spun in centrifuges.

5. Cellulose acetate in glacial acetic acid may be passed into a precipitation bath which consists of about volumes by weight of alcohol, about 25 volumes by weight of water, about 20 volumes by weight of ammonium nitrate and about 20 volumes by weight of sugar. The same swelling bath as mentioned in Example No. 4, may be used. The stretching takes place in the same manner as mentioned in Example No. 4.

6. A solution of acetyl cellulose in acetone or in strong acetic acid or formic acid is spun in a spinning bath which is composed of about /3 volume of phosphoric acid (83%), about A; volume of ethyl alcohol, and about A; volume of water (viscosity at 20 about seven times the same of water). One produces excellent strong threads. In such a manner, it is possible to spin acetic or formic acid solutions of cellulose acetate after having neutralized the mineral acid catalyzers by means of a buffer. The spinning of the acetylating mixtures was heretofore not successful, but it can be made so with the processes described herein. The stretching takes place during and after passing through the precipitation and swelling bath. For this should be considered suitable mixtures of solvents and non-solvents, in special cases, even the addition of precipitants.

7. Cellulose ether alone or mixed with cellulose esters may be formed into products of all kinds by proceeding in the same manner as described in the other examples.

I claim:

The process of manufacturing products including threads, filaments, ribbons, films and the like which comprises spinning a solution of cellulose nitrate in a bath containing about 17 to about 23% ammonium nitrate, about 24 to about 30% Water and about to about 56% alcohol to solidify said cellulose nitrate and form a solidified cellulose element, pulling oil said element at a rate of about 30 meters per minute with little stretching, passing said solidified cellulose element into a bath containing about alcohol to convert said solidified element into a plastic state, stretching said element and allowing said stretched element to dry whereby a cellulose element is produced having a dry strength of about 2.60 grams per denier, a wet strength of about 1.50 grams per denier, an elasticity of about 10% and a stretching of about 12%.

ERNST BERL. 

